The invention relates generally to vehicle parking brake detection and warning systems and more particularly to parking brake detection and warning systems adapted for air parking brake systems, such as air parking brake systems for locomotives.
Traditional parking brake systems typically include a lever which is connected to a cable or chain which actuates a parking brake mechanism to apply a brake when the lever is pulled. Parking brake detection systems are known which activate a dashboard light when a parking brake lever has been pulled, such as found in automobiles. Generally, the dashboard light notifies the driver that the parking brake lever has been activated so that the driver does not continue to drive the vehicle and consequently burn out the brakes.
Conventional parking brake systems for locomotives use a mechanical linkage mechanism which allows the operator to pull a lever or rotate a wheel which then pulls a cable or chain linkage to actuate a parking brake. A problem arises with known parking brake detection and warning systems in that such mechanically linked systems are often cumbersome to actuate given the mass and length of such linkages. In addition, the mere illumination of a dashboard or console light sometimes fails to adequately apprise the vehicle operator that a parking brake is activated. For example, in a locomotive, the operator may not be present in the cab during movement of the locomotive and, hence, may not be apprised of the visual indication of the parking brake activation.
Other locomotive parking brake systems are known which attempt to reduce the mechanical linkage of traditional systems. One such system is a spring applied/air release type parking brake system. These systems typically have springs that apply a brake shoe to a wheel in the absence of air line pressure. The parking brake is released when an operator opens a valve to allow air pressure into the air line to cause the spring to release the brake shoe. However such systems are not generally equipped with detection and warning systems to adequately apprise the operator of an improper parking brake condition.
Another problem with known parking brake detection and warning systems is that the parking brake may endure severe degradation as the speed of the vehicle increases. Therefore, it would be advantageous to have a parking brake detection and warning system which determines a warning condition based on vehicle speed and provides different warning levels dependent on the vehicle's speed so that the operator may take appropriate action.